Visual attention is the process of selecting a subset of incoming visual information for further processing. Attention is normally allocated either to a particular location in space (spatial attention), or to a specific feature, such as color or motion, at that location (feature-based attention), or to some combination of the two. While research has tended to focus on how the brain enhances or modifies the representation of visual stimuli within the spatial focus of attention, recent electrophysiological and neuroimaging evidence shows that attention can also affect the neuronal response to an ignored visual stimulus, if it shares common features with an attended stimulus. Also, preliminary studies show that attention to an auditory stimulus can also have a different effect on the brain's response to an ignored visual stimulus. The brain's processing of unattended information therefore depends strongly on what is being attended elsewhere. The goal of the proposed research is to use a combination of functional MRI and behavioral methods to obtain a better understanding of how the brain's representation of unattended stimuli depends on the location, feature, and modality attended to elsewhere. Findings from the proposed research could have significant impact on our understanding of attentional disorders, such as autism and ADHD, which may involve a disruption in the ability to ignore distracting sensory information.